The original population decided to do without money, so they created a central distribution system with record keeping, like the Feudal Japanese system. It is very efficient. It also allows for external bartering for credit.
No money? I am not familiar with the Japanese system you speak of. Gold or other precious items wouldn't be coveted then above other things? How does that work. Is there something specific to the world that makes itself innately valuable?
The Colonists came to Kerren with some Utopian ideals, as so many colonists going so many different places in human history have done. They came to Kerren to escape many of the problems of Earth. The foremost was high technology (admittedly Kerren's technology is a bit lower than they originally expected... darn electrosensitive Saurians). One of their others was living closer to the natural world, ecologial sensitivity and a non ownership view of land, (shepard view rather than owner view)
The Kabutz social model was a utopian one, and one of the few commune structures that have worked throughout history. It is also well suited for a lower technology level. By applying that model, they get a cooperative socialist structure (The step before Marxian Communism, not the kind certain revolutionaries actually implimented).
One of the keys of the Kabutz is a central warehousing and distrobution of goods. One of the others is minimal private property. In the Kabutz system, all decisions and allotments are made by the entire group. In Kerren, one person is the central coordinator. The Warden, the head of the ward, is the head of distrobution of resources in the Ward. He takes input in from the Senior/ Important members of the Ward, but he is the final word. He works with the High Warden and the central council of Wardens (in which the Warden is a part) to even out issues of equitable trade between Wards, should a ward have a need that the local people can not meet. The Central coordinator role is what makes this economic system more akin to the Nihon Feudal system, than Kabutz.
On Kerren, the locals acknowledge that Gold and certain gems are keen and somewhat more valuable than their utilitarian needs. However, this world has even fewer metalic resources that Japan or even Greece. If an economy is based on a material, there has to be enough of the material to use for the economy. There is not enough Gold on Kerren to make this possible. In fact, Iron would be the "precious metal" of Kerren. However, they really do not have enough of it to make an economy. Combine this with a bunch of silly utopians, and you get an initial economy that does not have money.
There really isn't anything organic that would substitute well. Organics is something that this planet has way, way too much of. (One of the reasons it was colonized).
So there system is one of Ledgers for big trade and Barter for little trade.
Every person gets a minimum amount of resources noted towards there name. To receive more resources, you are expected to produced for the Ward. When you make an expected amount, you recieve more goods. If you produce more than the expected amount, you get that extra alloted towards your name. You can then borrow against this, i.e. barter with them at the warehouse. So you make pans. You want blankets. You goto the warehouse and someone there checks the ledge, marking off one of your spare pans, for three blankets, or some listed trade rate. The whole system is a check and balance, double entry book keeping system.
Or you can take your excess and barter it with any excess others might have. You can do this in person, or by writing a draft and making the change in the central ledger.
If you have an excess, you can have a trader sell it somewhere else. paying a Ryder to transport it there. You can then trade those items for what you need.
Wardens sell larger lots of excess to other Wards that need them. Since a plauge a few generations back, not every location can make all their domestic needs. However, between the Kerren central economy and the fact that any amount of goods can be tranported anywhere in the world within an hour or two, this has not been a problem for the people.
One of the advantages of this is there are no "muggings" for cash or money. However theft becomes more important. However, Each Kerren Cluster or Outland Village is a fairly small places (1-3000 or 100-10), so you know who has what and everyone's business.
One thing I will be implimenting is a "slash" on the equipment list, much like the Beaver Marks used in Canada. FYI: Older shops in Canada mark the back of tags with slashes/ marks, showing how many Beaver Pelts it would take to buy this (Each one is about $12.50 Canadian last time I was there). This will give players, people used to using money, a general idea of how things are valued against each other.
One of the hardest things in this game environment will be breaking players of the "Money habit". L5R did an okay job of bringing this idea across, and it is the only successful game to do so.
Oh the Japanese Feudal system had money, it was not commonly used until the prevolance until the "merchant class" rose to prominence around the 1300s. Kerren does not need money because these people already had the technology of a credit/ inventory system.